A complete life-cycle test with zebrafish was carried out with different concentrations of the binary mixture 3,4-dichloroaniline and lindane under flow-through conditions. Length and weight of fish of the F-1-generation were reduced, even in the lowest test concentration of 2 mu g/L 3,4-dichloroaniline and 40 mu g/L lindane. The same effects were found in the early life stage test for the F-2-generation. In the mixture of 100 mu g/L 3,4-dichloroaniline and 40 mu g/L lindane, fish which were exposed for their whole life time stopped spawning, irreversibly; the fish population will become extinct. In an additional experiment, fish were exposed to the same xenobiotic concentrations after reaching maturity. In this case, egg production was reduced. Cessation of egg production occurs in a concentration of 200 mu g/L 3,4-dichloroaniline and 30 mu g/L lindane. Nevertheless, effects on spawning are influenced by duration of exposure and the life stages of exposure.